Respiratory failure
A drop in the oxygen carried in the blood is known as hypoxemia. A rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure results from inadequate gas exchange by the respiratory system. This means that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. The typical partial pressure reference values are oxygen Pa more than 80 mmHg (11 kPa). Carbon dioxide Pa must stay less than 45 mmHg (6.0 kPa). In clinical trials, the definition of respiratory failure usually includes increased respiratory rate. It also requires abnormal blood gases like hypoxemia, hypercapnia, or both. Evidence of increased work of breathing completes the clinical picture. Respiratory failure causes an altered state of consciousness due to ischemia in the brain.
Type 1 respiratory failure is characterized by a low level of oxygen in the blood. PaO2 drops below 60 mmHg with a normal or low level of carbon dioxide. Type 2 respiratory failure involves hypoxemia with hypercapnia where PaCO2 exceeds 6.0kPa. Type 3 respiratory failure is often referred to as peri-operative respiratory failure. It is distinguished by being a Type 1 respiratory failure associated with surgery. Type 4 occurs when metabolic demands exceed what the cardiopulmonary system can provide. Patients in shock experience respiratory distress due to pulmonary edema. Lactic acidosis and anemia can also result in type 4 respiratory failure. Type 1 and 2 are the most widely accepted classifications.
Conditions that reduce the flow of air into and out of the lungs include physical obstruction by foreign bodies. Reduced breathing may occur due to drugs or changes to the chest. Conditions that impair the lungs' blood supply include thromboembolic conditions. Right heart failure and some myocardial infarctions reduce the output of the right heart. Any disease which can damage the lung tissue fits into the category limiting gas exchange. The most common causes are infections, interstitial lung disease, and pulmonary edema. Low ambient oxygen at high altitude creates another pathway for failure. Ventilation-perfusion mismatch occurs when parts of the lung receive oxygen but not enough blood. Alveolar hypoventilation decreases minute volume due to reduced respiratory muscle activity. Diffusion problems prevent oxygen from entering capillaries due to parenchymal disease. Right-to-left shunts allow oxygenated blood to mix with non-oxygenated blood from the venous system.
Physical exam findings often found in patients with respiratory failure include signs indicative of impaired oxygenation. Accessory muscle use in breathing signals other signs of respiratory distress. Altered mental status appears as confusion or lethargy in affected individuals. Clubbing of fingertips is a visible sign of chronic hypoxemia. Peripheral cyanosis presents as bluish color on mucosal membranes or fingers. Tachypnea describes a faster breathing rate than normal. Pale conjunctiva may also appear during examination. People with respiratory failure exhibit other signs associated with the underlying cause. If respiratory failure is caused by cardiogenic shock, symptoms of heart dysfunction like pitting edema are expected.
Arterial blood gas assessment is considered the gold standard diagnostic test for establishing a diagnosis. This is because ABG can be used to measure blood oxygen levels directly. PaO2 measurements confirm the low blood oxygen level characteristic of all types. Capnometry measures the amount of carbon dioxide in exhaled air. Pulse Oximetry measures the fraction of hemoglobin saturated with oxygen. Imaging such as ultrasonography or radiography assists in the diagnostic workup. It determines the etiology of a person's respiratory failure. These tools help clinicians distinguish between different causes and severity levels.
Treatment of the underlying cause is required if possible. High-flow nasal oxygen serves as first line treatment for acute hypoxic respiratory therapy. Medication such as bronchodilators treats airways disease effectively. Antibiotics address infections while glucocorticoids manage numerous causes. Diuretics treat pulmonary oedema when fluid accumulation occurs. Respiratory failure resulting from an overdose of opioids may be treated with the antidote naloxone. Most benzodiazepine overdose does not benefit from its antidote flumazenil. Type 1 respiratory failure may require oxygen therapy to achieve adequate oxygen saturation. Lack of oxygen response indicates other modalities like continuous positive airway pressure. Mechanical ventilation becomes necessary if severe cases do not respond to less invasive methods.
Prognosis is highly variable and dependent on etiology and availability of appropriate treatment. One of three hospitalized cases of acute respiratory failure is fatal. Survival expectations vary based on the specific underlying cause identified. Management strategies significantly influence patient outcomes in critical situations. The availability of advanced care resources determines success rates across different populations. Early intervention improves chances of recovery compared to delayed treatment protocols.
Continue Browsing
Common questions
What is respiratory failure and how does it affect oxygen levels?
Respiratory failure results from inadequate gas exchange by the respiratory system. This condition means that arterial oxygen or carbon dioxide cannot be kept at normal levels.
How do Type 1 and Type 2 respiratory failure differ in blood gas values?
Type 1 respiratory failure involves a PaO2 drop below 60 mmHg with normal or low carbon dioxide levels. Type 2 respiratory failure includes hypoxemia with hypercapnia where PaCO2 exceeds 6.0 kPa.
What are the common causes of reduced air flow into the lungs?
Conditions that reduce air flow include physical obstruction by foreign bodies, drug-induced breathing changes, and chest wall alterations. Thromboembolic conditions impair lung blood supply while infections and interstitial lung disease damage lung tissue.
Which diagnostic test serves as the gold standard for confirming respiratory failure?
Arterial blood gas assessment is considered the gold standard diagnostic test for establishing a diagnosis. This method measures blood oxygen levels directly to confirm the characteristic low blood oxygen found in all types.
What treatments are used for acute hypoxic respiratory therapy and severe cases?
High-flow nasal oxygen serves as first line treatment for acute hypoxic respiratory therapy. Mechanical ventilation becomes necessary if severe cases do not respond to less invasive methods like continuous positive airway pressure.